Add an optional Smargon static positioner (chi/phi angles + rotation axes)
that is reconstructed into the NXmx sample transformation chain. Chi/phi are
appended at the innermost end of the chain (closest to the sample) for both
the goniometer and grid-scan branches, with axes defaulting to chi {0,0,1}
and phi = omega default {1,0,0}.
- SmargonPosition gains chi_axis/phi_axis (common/JFJochMessages.h)
- OpenAPI: optional phi_axis/chi_axis arrays; clients regenerated
- OpenAPIConvert wires Dataset_settings.smargon -> DatasetSettings
- CBOR serializer/deserializer round-trip the axes
- tests: CBORSerialize_Start_Smargon
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>